Customarily, door lock cylinder housing assemblies are secured within a through bore of the door by one or more machine screws passing from the inside of the assembly outwardly and also from the outside inwardly. From the standpoint of security, this arrangement leaves a lot to be desired because the exterior screws can be removed from the assembly and the remaining interior screw or screws are rather easily broken by continued prying or twisting of the exterior exposed part of the assembly.
Because of this defect in the prior art, the invention was created to provide a door lock in which the lock cylinder housing assembly is coupled or secured within the through bore of the door without machine screws or other separable fasteners, accessible from either the outside or the inside of the door. In a preferred embodiment, the housing parts are coupled by screw-threads within the confines of the through bore.
An intersecting dead bolt assembly in an edge opening of the door extends entirely across the door through bore at right angles to the housing assembly and also extends through a transverse passage in one of the housing sections so that the same is locked against rotation. A catch device in the housing assembly cooperates with a catch release mechanism on the bolt assembly to normally secure the interior lock cylinder housing section against removal. Only at such times when the door is open and its edge having the dead bolt assembly is exposed, can the catch device be released by the movement of a plunger means, preferably contained in the interior of the dead bolt.
Other features and advantages of the invention will become apparent during the course of the following description.